A full-line type print head comprises a plurality of nozzles that are arranged and is fastened to the main head body so that the array direction of the nozzles coincides with the direction of the paper width. An inkjet printing apparatus such as illustrated in FIG. 1 is able to perform printing by conveying a print medium with the print head stationary, so high-speed printing is possible.
One kind of technology related to driving print heads is time-divisional driving of nozzles as disclosed in Patent Literature 1, for example. Time-divisional driving is performed in order to improve the speed of supplying ink and the stability of the ink supply, and in order to reduce the amount of peak power for driving the print heads.
FIGS. 2A to 2C are drawings for explaining an example of conventional time-divisional driving. In this example, the printing apparatus is such that a plurality of nozzles that are arranged in a row are divided into a plurality of nozzle groups with 16 nozzles in succession in each group, and each nozzle of these nozzle groups is driven at different timing. In the time-divisional driving of this example, nozzles that are driven at the same timing exist in every 16 nozzles.
FIG. 2A illustrates the relationship between a nozzle array and nozzle groups. FIG. 2B illustrates the timing for driving the continuous 16 nozzles, with the nozzle position in the array illustrated along the vertical axis, and the time illustrated along the horizontal axis. The 16 nozzles in a nozzle group, for example, from nozzle 1 to nozzle 16 are driven in order according to the timing of one cycle illustrated in FIG. 2B, and are similarly driven for each continuing cycle (not illustrated in the figure).
During one drive cycle, dots are formed in the same column on a print medium (area of one pixel width), however, the print medium is conveyed during driving, so dots are formed at shifted positions due to differences in the drive timing. Therefore, for printing data in a line perpendicular to the conveyance direction, dots are formed being shifted and distributed a maximum of one column width from the ideal dot position (see FIG. 2C). A dot distribution such as this that is formed on a print medium is disadvantageous in printing black text for which quality is required at the edge of an image.
As technology for solving this problem, there is technology that sets the nozzle positions of a print head to correspond with the conveyance speed and the drive timing during time-divisional driving. In the same way as illustrated in FIG. 2B, the 16 nozzles in a nozzle group are arranged so as to be shifted as illustrated in FIG. 3A to correspond to the shift in the drive timing during the time-divisional driving illustrated in FIG. 3B and conveyance speed. As illustrated in FIG. 3C, with this kind of technology, it is possible to cancel out the shifting between the ideal dot arrangement on a print medium and actual dot arrangement that is formed on a print medium.